I find lines help me, some people will vehemently disagree with me, each to their own. I tried a lot of fretless basses over the years and thought it just wasn’t for me and assumed that was because it was so difficult but the difficulty came because I hadn’t found the right fretless. When I tried a 30” scale I found I could play it ok. So try lots of fretless basses and don’t give up if it’s too difficult, it might be you just haven’t found the right bass. I have lines and side dots, gradually you rely on them less and less as your ear improves. Some of the best advice I had on here was to just play the same as you would on a fretted bass, bass lines you are familiar with then you’ll hear when your intonation is out. For me the weird thing was after playing fretless exclusively for a couple of months, going back to a fretted bass felt very restrictive, fretless can be a very freeing thing. People will give you all sorts of advice and tell you their way is correct, there is no correct way, try out all the advice and settle with what form of practice suits you.