@linl
OK, it seems there are problems, meaning restrictions from maybe your country (or maybe USA, or both, I don't know where the download servers are hosted), that can prevent installer to download properly.
Another topic is already opened about this problem.
https://forums.ubports.com/topic/12174/mirrors-for-users-in-russia/21?page=2
I'll merge yours with it.
Please be patient, the issue is already known, but UBPorts team don't have much ressources (in any kind) to react like gafams can (but may not), and this may need a new version of installer, servers, mirrors, or whatever.
Feel free to read thread and continue here, and maybe go to the russian telegram UBPorts help channel mentioned in previous post.