Router Purchase 15+ connections advice

Hi, Long time lurker on this forum

I have a Linksys E4200 for some years that serve me well but its getting slow with so many devices.

2,4ghz band is failing i suspect its a harware issue.
5ghz Band its ok but has short range in the apartment
I also have a switch from Netgear GS308-100UKS connected/next to the E4200


By Ethernet CAT6
Synology DS412+ link aggregation, but its not priority
Anthem MRX
Cable Box
Satelite box
Oppo 103D
Nvidia Shield
Mede8er 1000x3d
Wetek core 4K
Apple...

Router Purchase 15+ connections advice