Sorry to see you're having issues after iOS 26.
I had no issues with iPhone 11 with either 26 or any point updates.
Barring hardware (storage) issues, I can only suggest you do the following.
- Back up your Photos to either a computer or iCloud
- Back up any files or application content to either a computer or iCloud
- Reset you iPhone (Erase Content and Settings)
- Set up as new (do NOT recover from the whole iPhone Backup - the first two bullet points do NOT mean "iPhone Backup to iCloud" feature, they mean you use iCloud sections to save Photos or Notes and any other content to iCloud, or hook it up to a Mac/PC and use Finder/iTunes as the backup tool for sections - not the whole device.) This is needed to "lose tail" of old and potentially corrupted Preferences.
- DO NOT install social network apps yet
- Restore Photos and bring back other content using iCloud "Save" sections or iTunes/Finder. Do NOT use "Restore Device / Recover iPhone" features that bring everything at once, including possibly corrupted Preferences or content.
- Observe behaviour for 2-3 days (leave it charging overnight so it indexes your content).
- Please report if this helped
The final steps involve installing social network (Meta) applications that are known to pervasively observe you. Do this little by little, only when you have established what the "clean" behaviour is like, so you have a baseline to compare to. Notice which apps slow it down. Consider deleting the apps and using Safari to respectful websites instead. You can Pin to Home websites like Facebook and X.
If your 'clean, no 3rd-party apps' iPhone works fine, this was not a hardware issue. If it does not, consider calling Apple, they can perform remote hardware diagnostics over internet even while you're on the phone.
Remember to do the first two bullet points properly if you're not OK with losing some of your data.
If this helped, suggested root cause is filesystem or file corruption. I have seen this happen with older versions, not sure how much had been fixed since. But the method above can give you "new iPhone feeling" assuming you will NOT restore iPhone but set it up as new and bring content only.
