Congrats, and a warm welcome to the FOMO-less club and to the omfg-had-no-idea-I-had-so-much-time-to-do-stuff club ;)
Imho, the most important tool/help anyone can get is to find other but as exciting stuff to do then to stare a the screen (phone or otherwise). For me, it was taking long walks (it also helped a lot put me back into batter physical shape), hobbies (like painting, scale models, music,…), or activities one enjoys and that don’t require the use of a screen. Cooking, writing, sketching, DIY, craft,…
The second most important tool would be to not hate yourself if/when you will fail. Try not to fail, obviously, but when it happens instead of hate and shame and anger (any impression this could be based on personal experience would be a pure 100% coincidence, this goes without saying) try to understand how and why you failed. So, you will be better prepared next time.
Edit like you mentioned, the support of your SO is a huge help too. My spouse was amazing in helping me get over my own addictions (not phone related, but addictions nonetheless).
They could have made a (second) fortune selling vaseline, or some water-based lubricant, to their customers.
The less ‘digital services’ in my life, the better.
edit: forgot a word :p