Generally, retrofit LED tubes come in two types: those where no modification to the luminaire is required (where IEC 62776 applies) and the more common type where some rewiring or bypassing of the existing control gear is needed.
In the latter, you rewire the luminaire so that the incoming mains goes straight to the lamp caps. Whether or not this is a good idea is a hotly disputed topic in the lighting world, and there is currently no specific safety standard for these lamps. However, there is general agreement among European laboratories that tests for these lamps should apply the appropriate aspects from related safety standards such as 60598, 61347 and 62031 together with a risk assessment and a detailed review of the modification instructions supplied.
Currently, most of the major lamp manufacturers build their LED tubes to meet the new IEC 62776 standard, but you should always check with your supplier.
Remember that IEC 62776 (and the other standards mentioned above) are about safety. They do not tell you anything about performance factors, such as light output, colour rendering, beam distribution or energy efficiency. There are good and bad ones out there, so it’s worth checking these details carefully too.