Not all artists are musicians. A shocker I know.
I will not name my customers on here, suffice to say that those who are musicians have not played anywhere due to Covid and no other reason.
You do not need an ATA carnet for Europe, they cost around £450 each. You can use Duplicate List which is free, would have thought the Musicians' Union would be aware of this, seems not though.
The process of touring Europe is now very similar to that of touring the US. You can no longer just wander in, play some gig, flog some tat and piss off home without a thought to paying taxes in your host country, you need visas to enter and you need to make sure you don't use the host country's facilities without contributing towards them. Of course America is easier in that respect as you only need one visa for the whole country, whereas currently you would need one for each European country you visit
I would have thought that you may take advantage of someone on your boards who actually does this shit day in, day out, but it seems in your world I know 'nothing' about this.