Drone tuning using the drones in the lessons works okay but I bought this years ago when they weren’t so pricey and have found a new use for one of its many features:
https://www.boss.info/us/products/db-90/
By selecting any desired note and turning up its speaker (it can be LOUD !) you can actually ‘feel’ the resonance and ‘beating’ when going off the correct intonation. You can slide up and down from the correct intonation and really ‘feel’ it ‘come in’ when you are spot on. I wouldn’t recommend it just for this use because of its price but if you have access to one it’s a fine practice tool.