Hi Alex,
There is currently a uservoice open which is under review by Microsoft to allow the importing of data from several alternative apps including Basecamp -
https://microsoftteams.uservoice.com/forums/555103-public/suggestions/16933120-importing-from-slack-...Would recommend to vote on it to push it up the agenda. It’s got a lot of votes, but it’s been some time since it was raised so I would say it could be some time until the functionality is there.
It would investigate a third party tool or look to do it manually. Another alternative would be - and this depends on your org, simply exporting the basepoint data and either archiving it or waiting for a time where Microsoft or a third party develop the tool to import the Basepoint data.
Doesn’t look like there is a great deal out there at this point in time for it!
Hope that answers your question!
Best, Chris