Hi I currently use bootlint but the latest version I could find was for Bootlint 3 - it kinda works with v4 but you have to ignore certain errors and I’m sure it is missing others.
Sorry I don’t use bootlint so don’t know much about it but from the documentation it looks as though someone is slowly working on v4 but seems to have stalled.
I just use the w3c css and html validators and there are also a number of js linters around if you google them.
At the end of the day bootstrap is just html, css & JS anyway