@Elizabeth Miller yeah this is a real thing to think about, especially with WiFi APs in close proximity — those can absolutely stomp on BLE if they're transmitting on overlapping channels.
The good news is that at 800m indoors you've got way more link budget than you actually need, so the module can absorb a fair amount of interference and still maintain a solid connection. That headroom is essentially your buffer against the noisy environment. Where I'd focus attention is less on adding external filtering and more on channel selection — BLE's adaptive frequency hopping will help, but if you've got a dense WiFi environment you want to make sure channels 37, 38, 39 (the BLE advertising channels) aren't sitting right on top of your busiest WiFi channels. Mapping your WiFi channel usage before the deploy is worth the 20 minutes it takes.
On the Zigbee side, that's also 2.4GHz and can create some packet collision issues depending on your Zigbee channel config — Zigbee channels 15, 20, 25, and 26 are usually the safest bets for minimizing overlap with both WiFi and BLE, so if you have any control over those nodes it's worth checking. As for external filtering, honestly for this use case I don't think you need it — the module's RF front-end is already designed with sensitivity in mind, and the link margin you have at 800m gives you enough room to work with. If you were pushing up against the edge of range in that environment it'd be a different conversation.
