Do free servers on https://aternos.org/ work?

I am planning to get Minecraft Java edition, and I want to make my own server for free. I looked up "Free Minecraft Server" and went to https://aternos.org/. It advertises it is free, and I made an account. I'm just wondering if this works, without putting myself at risk and getting any kind of spyware, PUP, or malware on my computer. Please let me know if it works or not.

<Note: This is also on my Reddit account, but it is not spamming. I just wanted more people to see my question, so I also posted it here :)>

The company claims to make money through ingame advertising.

Funding is done exclusively with the earnings from advertisements, there are no costs for the user.

[...]

We have created a unique in-game Minecraft ad format which reaches every Minecraft player that has a Minecraft server provided by us in their in-game server list. While the server is offline, we provide a custom MOTD (Message Of The Day) in the server list that informs the user about the current server status. This message can have up to two lines and we can use the second line for ads. It comes with some technical restrictions but is a unique and exciting way to reach Minecraft players.

Future will tell if this is a sustainable business model. But in case it is not, you should make sure that you have regular backups so you can move your world to another hoster.

Regarding the company itself:

They claim to exist for 8 years, and according to archive.org their website indeed exists since 2013 and indeed claimed to offer free minecraft servers back then. So if they run a scam, that would be a pretty elaborate long-con.

They also have an imprint which does not raise any obvious red flags.

• The company address in Germany exists on Google Maps (it's in a residential area, but starting a company from home is not unusual for a tech startup nowadays)
• They claim to be a "GmbH" which is a common company form for small and medium-sized businesses in Germany. A GmbH is a limited liability company with a starting capital of at least 25,000 €.
• It lists a complete name as company owner
• It lists a telephone number
• It lists a tax number and a business registration number which at least look syntactically correct.

All of that information could be made up, but it does hold up to an initial smell test and should be verifiable with some additional effort (which I am not going to invest).

To answer the question simply:

Yes

These free servers work. You can join them, your friends can join them, you can add plug-ins and mods (I can't help but recommend playing Origins mod with friends). Keep in mind that these will not be the highest quality servers and are only meant for you and your friends.

As opposed to what @Fredy31 said, there is in fact a premium solution (Yes this is run by the Aternos team). This premium, known as Exaroton, seems to be high quality, but I have not tested it myself. If their website is to be believed, the specs are fully customizable, for a price.