Is this because segwit adresses were only implemented with 3.0?
Yes. But why would you want to use an outdated version of Electrum? This version has multiple synchronization issues (besides some critical exploits and security issues).
Why don't you use the latest version? You should always keep your wallet up-to-date.
Also weird bug, when I type the seed of the wallet created with 3.1.3 to restore with 2.8.x at word 6 and half (!) of the seed suddenly the next button gets grey. When I click it it tells me I can restore a wallet with 2Fa now. When I click on this I get an error window with the possibility to send a bug report?
It probably thinks it's a 2FA wallet seed, but since it's not valid, it just crashes. Anyways, that's an old version.