Dury's Guns here in sunny San Antonio, TX has a number of firearms in their current web listings for sale online or in their shop. Most, if not all, of their online inventory is also listed on Guns International. I haven't personally purchased any firearms from Dury's.
https://www.durysguns.com
Collectors Firearms in Houston, TX has an always changing inventory of firearms for sale online and / or in their shop. Their primary focus is collectable items but they take items in trade so they have a diverse range of items in stock at any particular time. I have purchased a firearm online from Collectors Firearms and had a positive experience. This shop also lists on Guns International.
https://www.collectorsfirearms.com
Here's a link to Guns International. Lots of listings here by businesses as well as individuals. Items in the Cabela's Gun Library are typically listed here as well as on Cabela's website which I like because I really don't like the current (recently changed) layout for Cabela's Gun Library on Cabela's website. The filter and display options here have worked well for me.
https://www.gunsinternational.com
Here's the Cabela's Gun Library link, for sale online and / or in store. I have purchased a rifle from this system, from near the opposite side of the USA and Interstate 35 (Owatonna, MN) vs where I live (San Antonio, TX) with zero purchase hassles. I used their free ship-to-store option to the Bass Pro Shop in San Antonio where I live with zero shipping or FFL fees using that option. Included with my rifle was a gun lock and hard plastic sided foam lined gun case not spelled out in the listing. I'm not sure but I think that's standard at least for rifles purchased through this system. The rifle I purchased was shipped to the SA store in that case, inside a cardboard box that the shipping label and other labels were stuck to. A nice unexpected (by me) feature. Dunno the specifics on handgun shipping. My particular in-store pickup experience with this rifle was of a lower standard than firearms I've purchased online sent to my preferred LGS but that's just something to be endured at the gun counter at my local Bass Pro Shop. No shipping costs, no FFL transfer costs, and rifle case + gun lock at no additional cost balanced that out.
https://www.cabelas.com/shop/en/use...&pageView:grid&minPrice:&maxPrice:&pageSize:&
There's also Gunauction.com that previously had another site name I don't recall ATM. Not as well trafficked as Gunbroker.com and site navigation is somewhat clunky but I've purchased from listings on here.
https://www.gunauction.com
Others have mentioned Armslist.com
https://www.armslist.com
Plus there's GunsAmerica.com
https://www.gunsamerica.com
Atlantic Firearms primarily focuses on AK style firearms but has a mix of firearms available.
https://atlanticfirearms.com
Hope this helps. I'm sure there are plenty of other options, these are the first ones that came to my mind as a mix of B&M and listing services websites to post up their web links beyond Gunbroker.com which was already mentioned.