Hi, it's actually possible to sideload the apk from an android device. I've just tested it with my android phone.
First, you'll need to create a developer account and enable developer mode: https://aixr.org/insights/how-to-enable-developer-mode-on-oculus-quest-2/
For safe measure, you might need to enable developer options in your phone settings as well.
Next, you'll need to install the SideQuest app on your phone. Go to the play store on your phone, search for sidequest. Install the SideQuest ( BETA ) app by SideQuest Ltd. Launch the app, and then connect a usb cable from the phone to your Quest 2. Put on the headset, and confirm the prompts that ask for permission. In the SideQuest app on your phone, click on the three dots in the bottom right corner, then select "go to url". Type in "http://itch.io". It'll take you to the itch.io webpage. Login to your itch.io account, go to your library, and download the HereSphere apk. There'll be a prompt that asks for confirmation to install the apk to your headset. It'll take several seconds to download and install. Once complete, put on your headset, go to your app library, select unknown sources from the dropdown box in the upper right corner, then click on HereSphere to launch the app. Let me know if you have any issues or questions.
Edit: If you want to install SideQuest directly on your Quest 2 so you don't need your phone to install updated apks in the future, then that's also possible with the SideQuest android app. Click on on the three dots in the bottom right corner, then select "Install SideQuest into your Headset". SideQuest will now be available under unknown sources in your Quest 2's app library. The SideQuest VR app is a little broken after the v51 update, so the search icon is missing. You can click in the blank space in the upper right corner to open up a search box, though. Type in "heresphere", then select the app. Click on the "Download app (itch.io)" button. It'll take you to the HereSphere itch.io page. You'll need to figure out a way to login to your itch.io account. One way is to scroll all the way down to the community posts, click on a thread, then there'll be a login button near the bottom of the page. Login to your itch.io account, go back to the HereSphere itch.io page, and a download button should appear near the top of the page since you're logged in. Click on the download button, select an apk, and then SideQuest will download and install it. If you get a message saying something about enabling installing unknown sources, click on the message, and then enable the toggle. If HereSphere is already installed, there'll be a prompt that asks you whether you want to update the app.