I came across this video from W2NDG which shows the UV-K5 and a firmware mod running single sideband (SSB) on 17 meters. Check it out, pretty cool!
So I loaded the firmware myself to have a play with this mod which are listed below. If you get this mod working, let me know in the comments below how you did, the firmware version and model of Quansheng.
Firmware 
https://github.com/spm81/Quansheng_UV-K5/tree/main/Firmware/UNIVERSAL%20FIRMWARE%20(%20All%20Radios%20-%20UV-K5%2C%20UV-K5(8)%2C%20UV-K6%2C%20UV-5R%20Plus%2C%20etc…)/Open%20Spectrum%20Firmware%20by%20facgi
Telegram (Requires translation) https://t.me/s/quansheng_uvk5_spectrum
More UV-K5 Mods https://www.youtube.com/playlist?list=PLSuX83ay4Ouh_qMAC79F92DNVaOtywmC5
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