Universal Tweaks: 1.7.1 (https://www.curseforge.com/minecraft/mc-mods/universal-tweaks)
ConfigAnytime: 1.0 (https://www.curseforge.com/minecraft/mc-mods/configanytime)
MixinBooter: 8.3 (https://www.curseforge.com/minecraft/mc-mods/mixin-booter)

When trying to install Universal Tweaks on a Aternos Server, the required dependency mod ConfigAnytime is not available to install.

Aternos download options for Universal Tweaks

• ConfigAnytime is not shown as a required Dependency: https://aternos.org/addons/a/curseforge/universal-tweaks
• Without ConfigAnytime, the server will not start with Universal Tweaks installed.

Attempted fix through Aternos

1. I attempted to suggest the ConfigAnytime mod to Aternos (https://aternos.org/suggest) and got the message "This is not popular enough".
2. I followed this by sending a email to Aternos support, noting that the ConfigAnytime (almost 10k downloads) is a required dependency for Universal Tweaks (which has over 252k downloads).
3. Followed up with a discord post on Aternos channel: https://discord.com/channels/107936397578489856/1064609403178856459/threads/1136788291639857284

Options without Aternos

1. Use Universal Tweaks 1.6.0, rather than the latest version.

• You must downgrade MixinBooter to version 7.
• You lose any updated functionality done after Universal Tweaks 1.6.0 and MixinBooter 7.

2. Use a different server hosting (such as FalixNodes).

• Aternos is one of the most popular free hosting sites due to its ease of use. Many users may be discouraged by the learning curve to switch hosting sites.

4. Change Universal Tweaks dependencies to no longer require ConfigAnytime (making it optional).

• Requires changes to the mod and the work that goes with that. May cause functionality loss in features.

Sorry, but I can‘t take responsibility for the policies of other hosting services. ConfigAnytime is the foundation of almost all configurability and solved the most scuffed technical part of Universal Tweaks and I won‘t go back to previous means, I‘m afraid.
So the only advice I can give you is to keep 1.6.0 for the time being, keep on pestering Aternos people or use alternative hosts.

Aternos just added ConfigAnytime to its download options. Issue resolved. Thanks for the suggestion ;)