Mapy.com does that really well [0] (not affiliated). Not open source though. It uses mix of sources - OSM included - to render map (best render imo - especially the "outdoor" layer) and they are pretty large contributor to OSM in Europe. In free tier you can have one country downloaded for offline use. Sharing .gpx is no problem. Traffic data only in Central Europe.
Nobody has mentioned, that FreshRSS [0] has built-in web scraper too. It is also easier to use (little bit, imho), than changedetection.io. Works like a charm for me - mostly window shoping thrift shops.
Everybody seems to do stuff like this nowadays. Myslef included. I did have old K4NT lying around and started playing with it. With a little bit of help of AI (not for jailbreaking though! - lots of nonsense) I was able to put up little server, which now serves family calnedar agenda, but it is designed to be modular and I will put more stuff to it later. I've even designed and 3D printed insert into Ikea 12x18 frame and put a small "blade" powerbank with MagSafe to the back, so now I need to push powerbank button every 5 days. Internal battery is in a bad shape now, but I saw I can still buy an replacement. Wired version was not an option in my case.
I use Nextcloud Notes for that. It has decent mobile app and works great with few notes (Nextcloud Notes doesn't work as second brain very much).
I have two notes in there - Buffer and Shopping list. Buffer is one note for all the small stuff you mentioned. I also have widget on phone homescreen for that note so I can access it pretty seamlessly.
Of course, it also means, you need to access some Nextcloud instance (I run my own).
Edit: I use Obsidian synced with Nextcloud for all the "second brain" things.
[0]: https://mapy.com