I never get SMS text spam on my phone. Installed Lineage OS on a Samsung Galaxy S4 mini phone. I installed TWRP and LOS both from official website (not various links on google or XDA). Installed F-droid (with privilege extention).
I only had a handful of apps installed: Fennec F-Driod, Firefox Focus, Stocks Widget, Net Guard, net Monitor, BlueBourne Scanner, Termux, SnoopSnitch and Yalp,
Phone was running without a SIM for about a week. All was OK until I inserted a SIM. Moment I insterted the SIM a got spam from a load.
Note I have used the same apps (except for Fennec) on another phone without a single spam SMS!
So is the nightly infected with malware or spyware?