hey, i already own one of this devices since a long long time and im looking for a second dumb ap. it is in my opinion on of the greatest openwrt devices i ever owned (support is going on since years and i dont see support will stop any time soon).
the price is like 20€, which is also very cheap.
im asking, because there might be a better option in 2022?
The tl-wdr3600 is still very well supported and I don't see that changing anytime soon, however 8 MB flash are quite limiting.
Apart from this, 802.11ac (and ax) brought quite major -tangible- performance improvements (especially on the 5 GHz band), rendering 802.11n (what the tl-wdr3600 can do) pretty much obsolete. In a way, keeping 802.11n APs active 'litters' your airtime, forcing everyone on the channel to wait for the slowest (802.11n) participant. Therefore it does make sense to look into different hardware (or even replacing existing pre-802.11ac/ pre-wifi5 APs), even though they're still well supported by OpenWrt.
Used ipq40xx and mt7621a devices (ipq806x, if you're very lucky) can sometimes be scored in that rough price range as well, providing much better specifications.
While I still own a tl-wdr3600/ tl-wdr4300 myself, I wouldn't buy another of them today (and have mostly retired them for half a decade already, good as backup, for quick experimenting, but not productive use)