It's best to call Canon (I mean the headquarters in Japan, of course) and ask when they will release a can that would be suitable for testing their RF lenses in Poland. It seems to me that they need to explain the situation, describe the problem with testing lenses on the most serious Polish industry portal, and let them do something about it, maybe just build a special camera only for testing, because it can't be like now there must be such a backlog of tests.
Well, unless Canon wants to hide something, e.g. some specific defects of their lenses and that's why they haven't made a camera so far that would allow them to test their lenses - there may be something to it, such a theory makes sense in my opinion, they just don't want to spoil themselves interest and lose market share in Poland and Europe, which is why they are scheming and there are only cameras on the market that are not suitable for glass testing.
Something needs to be done about it, as they removed the most famous mailbox in the country, a living advertisement of Poczta Polska, we immediately acted at the source and the box returned to its place, continuing to serve the masses of photographers - now something needs to be done and as I say, it's best to attack Canon and either call or write an e-mail or several e-mails. If we all start writing to them, there is a chance that not everything will fall into spam, they will read and maybe change their policy towards cameras, and there will be at least one on the market where you can test the lenses.