No, you said only service providers, citing two of the biggest firms in tech.

Unfortunately, the rule is far more general than that. Anyone selling any sort of digital services or products online is covered, even if it's just someone selling crosswords from their kitchen table that are then supplied in electronic form.

You can't advertise as "9.99EUR + VAT"?

Technically, probably not. For B2C sales, prices are typically supposed to be shown VAT-inclusive according to the various consumer protection rules. Naturally that is difficult if you don't yet know what the applicable VAT rate is.

Or guess the VAT rate based on geo-IP location association?

You can guess, but that infamously is not a sufficient standard of proof of customer's location for the required record keeping, so you might have to change your mind later. For the reasons above, that can cause compliance issues of its own.

There are other problems with relying on IP-based geolocation as well. For example, some EU member states have regional variations in the applicable VAT rates for the same products or services. To the best of my knowledge, no IP-based system yet exists that has sufficient accuracy to cope with that. In fact, even within the regions they do cover, most such systems are expected to give the wrong answer perhaps 10% of the time because proxies, VPNs, errors in the underlying IP-to-location database, and so on.

There are plenty of other problems with the new VAT system as well. We haven't even talked about being accountable to and subject to audit by the tax authorities in every member state, or the number of such states that have already sent out mass demands for incorrect tax revenues under threat of immediate legal action if they aren't paid, in some cases even demanding payment faster than the receiving small business could reasonably take legal advice to make sure it wasn't their mistake.

The whole VAT mess is just a giant screw-up, a set of rules designed after long and expensive debates, perhaps conceived with noble intentions, but ultimately implemented with horrific incompetence. Unfortunately, the same could be said of various other recent EU rules affecting small businesses, consumer protections, and related areas as well.