In my experience, you dont need to drop $30 on a dbrand for the outer screen. I have tried many over the years and usually go with <a href=" https://www.ebay.com/sch/i.html?_nkw=Supershieldz+Tempered+Glass+Screen+Protector+2-Pack+for+ OnePlus+Open&_sacat=0&_from=R40&_trksid=p4624852.m570.l1311&mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5337998953&customid=22&toolid=10001&mkevt=1" target="_blank" rel="nofollow sponsored">Supershieldz Tempered Glass Screen Protector 2-Pack for OnePlus Open because they are cheap and thin. Usually under $12 on Amazon. They ship from midwest hubs so it hits Chicago in like two days. The fit is perfect even with bulky cases.

Jumping in here, been very satisfied with these two for consistent quality:

• Spigen Glas.tR EZ Fit Tempered Glass utilizes an auto-alignment tray which ensures a centered fit. The glass quality is superior and doesnt mess with touch response.
• Whitestone Dome Glass EZ Tempered Glass is engineered to be slightly thinner, providing maximum compatibility with high-clearance cases. Both ship quickly to the Chicago area and wont obstruct the hinge.

Like someone mentioned, cheap glass works, but I'd suggest the <a href=" https://www.ebay.com/sch/i.html?_nkw=Ibywind+Tempered+Glass+Screen+Protector+for+ OnePlus+Open&_sacat=0&_from=R40&_trksid=p4624852.m570.l1311&mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5337998953&customid=22&toolid=10001&mkevt=1" target="_blank" rel="nofollow sponsored">Ibywind Tempered Glass Screen Protector for OnePlus Open. I almost scratched my bezel with a bad alignment kit once, so it's best to watch it closely.

I am totally in the same boat, just got mine yesterday and i am genuinely terrified of scratching that outer display. Spending this much on a device is stressful as hell lol. I have been researching the same stuff and it is hard to find something that doesnt have reviews saying it peels off with a case. Basically i have been looking into the <a href=" https://www.ebay.com/sch/i.html?_nkw=Ringke+Dual+Easy+Film+Screen+Protector+for+ OnePlus+Open&_sacat=0&_from=R40&_trksid=p4624852.m570.l1311&mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=5337998953&customid=22&toolid=10001&mkevt=1" target="_blank" rel="nofollow sponsored">Ringke Dual Easy Film Screen Protector for OnePlus Open because it is a film rather than glass. Glass protectors can sometimes be thick enough to interfere with how the case clips onto the front frame, which is a huge pain on foldables. Film is way thinner so it basically disappears once it is on. It is usually cheaper too, which fits your budget. These usually have a specific install kit that lets you align it before the final adhesive touches the screen, which helps with the fit.