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'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
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.