There are always uncertainties regarding visas for Oman. This is because the visa rules have changed in recent years, but also because there is a lot of unclear or even false information on the internet.

I would therefore like to present the current rules here.
Your passport must be valid for at least six months at the time of entry.
Different visa rules apply depending on nationality.

The following conditions apply for 103 countries (see list below), including all EU countries:
You do not need a visa for stays of up to 14 days / 13 nights.
You will receive a stamp in your passport upon entry, which documents your date of entry. If you have been in the country for longer than 14 days when you leave, a fee of 10 OMR / day will be charged. This stay cannot be extended.

For stays longer than 14 days, you must apply for an e-visa online with the Omani police.
The link: https://evisa.rop.gov.om/.
This visa authorises entry within 30 days and is then valid for a stay of 30 days from the date of entry. You should therefore apply for it a maximum of 30 days before entering the country. Otherwise it expires.

This visa can be extended 2 times. However, this is only possible a few days before the visa expires. You can extend it online via the ROP portal or go to one of the DGPCS offices of the Omani Police ROP (e.g. in Seeb) and have it extended there. Please note the opening hours!
The e-visa currently costs OMR 20, as does each extension.

The previously offered visa on arrival no longer exists.
All regulations, such as insurance cover with Covid coverage, proof of hotel booking or a return flight ticket…. have been abolished by the Omani government for some time.
Nevertheless, the airline ground staff may still ask for it. This is not legal and will rarely happen.
It is advisable not to have an Israeli stamp in your passport