I know what you mean, you mean the software for SDRs is mostly geared towards tuning to 1090 MHz and decoding ADS-B pulses there.

But to be clear: the SDR's tuners are rarely limited that way. Most can tune to 978 MHz even easier than 1090 MHz. Covering the entire VHF to UHF range is pretty typical.

When I've set up P25 receivers, it's common to use 2-4 RTL-SDR's to do the bulk of listening. Each rtl-sdr gets set with a different center freq, and the control channel tells when and where to listen.

You can build a P25 listener for less than $100.

which software do you use to demodulate P25? gnuradio?

I use https://github.com/robotastic/trunk-recorder

You'll use https://www.radioreference.com and get the appropriate control and voice channels for your area. You'll also get the talkgroups and put them in a CSV.

From there, you'll use http://garvas.org/trunk-recorder/ to determine how many RTL-SDR dongles (or others) you'll need, along with their respective center frequencies. Note that you'll copy/paste the relevant control/voice line for your p25 from radioreferece.com

From there, just define where to store the files on the drive, and off it goes. There's a python webserver ( https://github.com/ScanOC/trunk-player ) you can install for on-prem, and/or you can also upload it to openmhz website ( https://github.com/robotastic/trunk-recorder/wiki/Uploading-... ).

Not OP, but thank you! I recently got a SDR dongle and was going to set it up. This will help.

Not difficult at all:

https://www.adsbexchange.com/how-to-feed/adding-978-mhz-ads-...