fyi, I would be happy to help in any way, I am a web developer and recently started dabbling in app development as well, don't hesitate to contact me I. case I can help
I'm using it too, but the eNB/gNB only correspond in Sunrise network, with 35/535 being GE, 20/520 - VD etc. in Swisscom and Salt, the antenna IDs provided by Confederation do not correspond to the eNB/gNB on the network itself, so it's quite difficult to estimate the correspondence between those.
I also know of LTE Discovery, as well as Open signal, but so far, Cellmapper is the best for me