As to the question about Coptic Orthodox communing in Latin Churches,
Canon 671, CCEO
2. If necessity requires it or genuine spiritual advantage suggests it and provided that the danger of error or indifferentism is avoided, it is permitted for Catholic Christian faithful, for whom it is physically or morally impossible to approach a Catholic minister, to receive
the sacraments of penance, the Eucharist and anointing of the
sick from non-Catholic ministers, in whose Churches these sacraments are valid.
3. Likewise Catholic ministers licitly administer the sacraments of penance, the Eucharist and anointing of the sick to Christian faithful of Eastern Churches, who do not have full communion with the Catholic Church, if they ask for them on their own and are properly disposed. This holds also for the Christian faithful of other Churches, who according to the judgment of the Apostolic See, are in the same condition as the Eastern Churches as far as the sacraments are concerned.
Canon 844, CIC
§2 Whenever necessity requires or a genuine spiritual advantage commends it, and provided the danger of error or indifferentism is avoided, Christ's faithful for whom it is physically or morally impossible to approach a catholic minister, may lawfully receive the sacraments of penance, the Eucharist and anointing of the sick from non-catholic ministers in whose Churches these sacraments are valid.
§3 Catholic ministers may lawfully administer the sacraments of penance, the Eucharist and anointing of the sick to members of the eastern Churches not in full communion with the catholic Church, if they spontaneously ask for them and are properly disposed. The same applies to members of other Churches which the Apostolic See judges to be in the same position as the aforesaid eastern Churches so far as the sacraments are concerned.
(The final sentence of quoted text from both the above canons refers, for the moment, only to the Polish National Catholic Church in the US.)
That said, the Catholic Church recognizes that reception of the Mysteries by Orthodox Christians is contrary to the expressed discipline of their own Churches in many instances and recommends that the Orthodox faithful observe the dictates of their hierarchy in these matters. The objection to such is pretty much the norm among the Eastern Orthodox Churches, but the situation with the Oriental Orthodox is more complex.
I won't presume to state the current the current discipline of the Copts on this matter. There was, at one time, an informal agreement between Rome and Alexandria intended to assure the adequate provision of pastoral care to Copts separated from their own churches. I believe that it was principally intended to benefit Coptic Catholics who, outside their historic homelands, have significantly less pastoral resources available to them than do their Orthodox brethren. Whether that agreement is still viable, I'm uncertain - but doubtful, However, the allowance for Coptic Orthodox to commune in a Catholic church certainly exists under the cited canons - with the onus resting on the individual as to whether such is permitted by his Church.
As to others of the Oriental Orthodox Communion, the longest-standing formal pastoral provision exists between Rome and the Syriacs, being primarily intended to serve the two Syriac Churches, Catholic and Orthodox.
In the Middle East, particularly, the agreement involving the Syriac Orthodox is informally extended, principally to the Melkites, although reportedly also to the Maronites in some places. However, relationships between and among the Apostolic Churches in the Middle East generally, Catholic and Orthodox - both Oriental and Eastern, are significantly more accepting and informal than elsewhere; it isn't hard to understand that the nature of being a minority at risk has contributed to building such a collegial attitude.
The Jacobite Syrian Orthodox Church (the Patriarchal faction), although not a formal party to the agreement, seem to indicate that they would honor it by reason of the Patriarch having entered into it.
The Malankara Orthodox Syrian Church (the Catholicos faction), on the other hand, would be unlikely to consider themselves parties to or bound by the agreement.
The Armenians, with their long history of cordial relations with Rome, have had such an agreement in place for many years. It is, to the best of my knowledge, informal (one periodically sees it referenced as being formalized, but I know of no one who claims to have ever seen the text of such).
Neither the Ethiopians nor Eritreans have any such agreement, formal nor informal, and I doubt either to be particularly receptive to the idea.
Albeit they are not truly 'Oriental Orthodox', the Assyrian Church is party to a formal pastoral agreement, virtually identical to that between Rome and the Syriacs. It is intended to be for the benefit of the Assyrian faithful and those of the Chaldean Church.
That agreement (probably less necessary than it was when forged, given the increased number of parishes that each Church now has in the diaspora) is still in place, although it likely suffered from the controversy surrounding the reception of Mar Bawai (Soro) into communion with the Chaldean Church. The Ancient Church of the East is not a party to the agreement and I don't know its formal attitude toward it, but I have read things which suggest that it is not strenuously opposed to the praxis.