Update 28 December 2022 an application to vary the August order on grounds of comity has failed:  ScotCS CSOH_94.
Update 3 September 2022 In  CSOH 57 on 22 August Lord Braid granted an anti-suit injunction , ordering James Finlay to continue its own attempts at obtaining an anti-suit injunction in the Kenyan courts, aimed at halting the Scots collective proceedings. Lord Braid referred ia  to the seminal Turner v Grovit case, of Brussels Convention fame.  James Finlay are found, in seeking and obtaining the Kenyan orders to have been vexatious and oppressive of the group members, whom its conduct was calculated to harass.
Update 3 February 2022 thank you Russell Hopkins for alerting us to the judgment of Lord Weir  CSOH 1,  that the suit meets with Scottish collective action /group proceedings rules. Forum non conveniens arguments will be heard later.
I posted the Tweet below in October, and am posting mostly to report that I do not as yet have more to go by. The suit is against James Finlay and follows in the footsteps of one brought in 2017, pre-Brexit therefore. The 2017 action per CJEU Owusu v Jackson cannot be subject to a forum non conveniens challenge, and I am as yet not aware of an Article 33-34 Brussels IA ‘forum non light’ defence. This new, 2021 action has already been said to be met with a forum non challenge. It will be interesting to see first of all whether the forum non challenge in the latest suit will be impacted by the unavailability in principle of forum non in the 2017 suit; additionally, whether defendants are aiming to have the 2017 suit thrown out on the basis of A33-34 BIa (so far I have not seen indications that they will).
As I point out in the Tweet, had the UK been allowed to join Lugano, forum non would not be available to this newest suit.
EU Private International Law, 3rd ed. 2021, Chapter 7.