Prague looks as a possibility. They already had speedway meetings in Czech with 400-500 crowds.
Togliatti indeed very unlikely... would have been nice though. Great place.
Maybe Vojens?
Updated FIM calendar:
08.08 - Final 1 - Forssa
05.09 - Final 2 - Morizes
20.09 - Challenge - Roden
26.09 - Final 3 - Rzeszow
Updated FIM Europe calendar:
01.08 - Solo Quali - Tayac
16.08 - Solo Final - Leamington Spa
06.09 - Sidecar Final - Pfarrkirchen
Extraliga will have crowds (25%) from the second round in the stands.
https://sportowefakty.wp.pl/zuzel/884104/pge-ekstraliga-kibice-wejda-na-trybuny-juz-od-19-czerwca
Vojens seems to be postponed according to the ticket sales page: https://www.billetlugen.dk/2020-tauron-speedway-euro-championship-billetter.html?affiliate=DKA&doc=artistPages%2Ftickets&fun=artist&action=tickets&erid=2702468&fbclid=IwAR0rUdbuD07So07I9YcRwBZHbIuOpF3xsATHsQWEcNfQyLQYsLAsn-eRt3M
Nothing official from One Sport or FIME though.