

the benefit of it is just not bloating my 128gb phone to it´s limits
That’s kinda the thing though, using modern codecs there’s no way you’ll get anywhere close to facing this issue. A song encoded with Opus at higher than necessary quality is 2.5 MBs on average - that’s over 20 thousand songs in 50 GB, not even half of your total storage gets you 50 days of continuous audio.
openWRT is fantastic and does indeed give you full control over your router… but not your modem. Modems are a complete mess of patents and proprietary software that nobody can control but a select number of companies.