Possibly someone make a recording and forward it to next person who will play back the recording and record their own voice and combine them, and send to next one, and so on. (Possibly the first recording might be the piano or organ, or whatever musical instruments you are using, if any.) This isn't as good as doing it with really choir, but for now, this is how you will have to do. Once the virus is go away enough then you can try to resume the proper way. (If you wish to use my suggestion, ensure that you must use a lossless codec, or else you could use a lossy codec if you manage the files carefully in a way to ensure nothing is encoded more than once.)

Like Eric Whitacre’s virtual choir? https://ericwhitacre.com/blog/the-virtual-choir-how-we-did-i...

Mixing many audios across the internet is hard, I've worked on this space before.

Best option is to send around multi-track files so you can play everyone but yourself, then mix you in and pass around.

never happen. latency would make it extraordinarily difficult even on isdn lines, and jitter on anything else ... just no. sorry.

Adopt a barn as practice space and spread out and shout.