"Note: by default, Notabase has a cap on the number of notes you can create. You can circumvent this by inserting an active subscription for your user id in the subscriptions table."
Maybe it's unclear, but you just need to insert a row in the subscriptions table with the value "ACTIVE". You don't actually need to have a real subscription on the hosted version of Notabase.
Besides, if you know how to code, it's simple to change the max number of notes to something like Number.POSITIVE_INFINITY anyway - but adding a row in the database is likely easier so that's what I recommend.
It may be a bit of a hassle, but I do this because the codebase for the hosted version and the self-hosted version is the same, which makes it easier for me to maintain. In the future, I may make a separate self-hosted version so that this step can be skipped.
Not really "self-hosted", then.