In order to have more flexibility of angles and poses this was not trained on a single tag like "69". Instead, you should use a combination of tags to achieve the desired effect. Although it is more complex to use, it allows for more freedom and without bias towards a certain angle. Different aspect ratios also impact the end result. As with SD image generation in general, what you tag in your prompt is what you want visible. With that in mind here's how you can use this lora.

Main base tags for lying 69 pose: lying, on back

Tags for types of actions: ???????????, ?????????, ???????, fellatio

Tags for a view ??????????? the female character: ???????????, ???, ?????, looking back, implied ????????, implied handjob

Tags for the female character facing the viewer: facing viewer, looking at viewer, ?????, ????????, ???????, implied ???????????, implied anilingus

Upside-down 69 tags: lifting person, upside-down, ????????, ???, back, ??????????? (this is a very complex pose for SD and tricky to generate, so it may require more tweaking, trial and error. It may actually require a separate lora to see if it performs better)

Recommended quality tags: score_9, score_8_up, score_7_up, score_6_up. Optional: source_anime

Recommended negative tags: score_4, score_5. Optional: 3d, lips, realistic

Note that the end result ultimately depends on the base model used.