I cannot reproduce this… when testing this on my server, Plex immediately let me set dates in 1890 etc. (PMS 1.23.3.4712, macOS 11.4). This worked for me using Plex Web (https://app.plex.tv/desktop) or the desktop client on my Mac. Working the same for movies or albums.
I haven’t seen any references about an issue fixed with the latest beta – so I’m not sure if updating to .4712 will fix this for you.
Does this issue persist if you restart your server?
Original Date (like Original Artist, Original Album, etc) refers the date when the original work was released, it doesn’t refer to when this recording was first released - that’s covered under the Release Date field. Or at least, that’s how the tag specs are written, it could be that Plex uses a different definition.